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An apology for primary repair of tetralogy of Fallot
An Apology for Primary Repair of Tetralogy of Fallot Glen Van Arsdell and Tae-Jin Yun The first repair of tetralogy of Fallot (TOF) was 50 years ago, so it would seem that the details for optimal management strategies would be clear. Timing of repair and operative repair strategy for TOF are still a source of debate. Varying institutions have published excellent outcomes with a primary repair strategy or a selective staged repair strategy. In this article, the current and historic strategy for repair of TOF at the Hospital for Sick Children in Toronto is delineated along with associated outcomes. Data from our institution indicate a clear survival advantage for primary repair of TOF. Semin Thorac Cardiovasc Surg Pediatr Card Surg Ann 8:128-131 © 2005 Elsevier Inc. All rights reserved. KEYWORDS: Tetralogy of Fallot, Blalock-Taussig shunt, cyanotic heart disease
Historical and Present Surgical Strategy Age for planned repair of TOF at the Hospital for Sick Children, Toronto in the 1970s through the mid 1990s was 18 months. Infants who were symptomatic before 1 year of age received a Blalock Taussig (BT) shunt and then the usual repair at 18 months of age. In 1996, repair strategy was shifted to one of elective repair at 6 months of age. Earlier primary repair is now performed if the child is symptomatic.
Rationale for Change to Primary Repair The change in strategy was brought about by analysis of institutional outcomes at two different time points. For many years, our institutional data and data from other institutions had shown that younger age at repair was a risk factor for mortality. This concern and some isolated experiences led to continued use of palliation as the first line of therapy for babies ⬍1 year of age. However, palliation was not without its own problems— overcirculation (sometimes causing death), pulmonary artery distortion, shunt thrombosis, shunt seromas, and interval mortality before repair occurred. Problems associated with palliation allowed for an “extra” net mortality margin if one were to shift to primary repair in infants who were thought to be at higher risk. At our institu-
From the Hospital for Sick Children, Toronto, Ontario, Canada. Address reprint requests to Glen Van Arsdell, MD, Hospital for Sick Children, 555 University Ave, room 1525, Toronto, ON, M5G 1X8 Canada.
128
1092-9126/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.pcsu.2005.01.016
tion, the outcomes benefits from the change in strategy are clear. Along the way we have learned that some of the improvement in outcome may be specifically related to repairing before excessive development of ventricular hypertrophy (ie, earlier repair was actually a protection against an unfavorable outcome).
Outcomes in an Era of Palliation Vobecky et al1 published our data for repair of isolated TOF from 1978 through 1988. There were 237 infants with the entry criterion being diagnosis (not procedure). Actuarial survival at 10 years was 89.5%. There were a total of 22 deaths, of which 14 were pre-palliation, at palliation, or postpalliation but before repair. Operative mortalities occurred in 7 of 218 patients (3.2%). There was one late death in the cohort. When we looked at the incidence of a transannular patch, it seemed that a BT shunt did not have an influence: Transannular patch occurred in 48% for those with previous palliation and in 54% for those without previous palliation. Fifteen percent of those having a BT shunt required a pulmonary arterioplasty at the site of shunt insertion into the pulmonary artery. Based on mortality data alone, one could make an assumption that even if earlier repair were associated with a higher operative mortality, the net change in outcome would be zero provided the operative mortality was ⬍8.9% (14 pre-repair deaths ⫹ 7 operative deaths/237 ⫽ 8.9%). The net change in years of life lived would be greater for any operative mortality of ⬍8.9%. The data became even more compelling if one looked at the10-year survival for the 19 neonates requiring palliation (77%). This fact gave further weight to primary
An apology for primary repair of TOF
129
Institutional Policy Shift Synthesis of the above data and rationale led to a change in strategy for repair. Our current strategy is repair at 6 months of age if asymptomatic. A child with saturations of ⬍80% will undergo earlier repair, as would a child who has a tetralogy spell or a suggestion of a spell. Symptomatic children are placed on propranolol, and an elective date for repair is scheduled.
Outcomes for Primary Repair Analysis for Optimal Age of Repair for Tetralogy of Fallot Figure 1 Right pulmonary artery stenosis seen at the site of the previous shunt insertion. Some degree of stenosis can be seen in up to one third of shunted patients.
repair because there was an even greater added “margin of safety” for the very young. Nevertheless, in the late 1980s and early 1990s, it was not a given that primary repair of neonates and very young infants would be less than 10%. Neonatal repair, for most institutions, was just becoming a reality. However, the mortality “hurdle” to cross seemed to be approaching an era-adjusted reasonable number.
Outcomes Related to Blalock Taussig Shunts In a second analysis of outcomes related specifically to BT shunts for TOF, Gladman et al2 evaluated 60 infants who had BT shunts between 1990 and 1994. Each patient had had cardiac catheterization before repair of TOF. A comparison group of 68 nonpalliated but repaired TOF infants who had had cardiac catheterization was also analyzed.
Significant Findings in Palliated v Nonpalliated Infants The right pulmonary artery index was significantly smaller in the shunted infants than in those who were not shunted. The discrepancy was greater for those who received their shunt during the neonatal period (0.84 v 1.05). Shunt-related morbidity was not inconsequential—there was a 28% shunt related complication rate (excessive pulmonary blood flow, 28%; seroma, 1.5%; Horner syndrome, 3%; diaphragmatic palsy, 3%). One third of patients had more than mild distortion of the pulmonary artery where the shunt was inserted. There was one late death caused by shunt thrombosis. Overall survival in the palliated group was 90% v 97% for those not having palliation (P ⬍.05). Although one can argue that pulmonary artery distortion issues (Fig 1) may be surgeon dependent, problems with overcirculation and a definable incidence of shunt thrombosis are institution independent. The latter are related to intrinsic physiology of BT shunt palliation.
The change in strategy undertaken in Toronto yielded an opportune time to analyze optimal age for repair.3 From January 1993 to June 1998, 227 children underwent repair of isolated TOF. During that time, median age of repair dropped from 17 months to 8 months (it is currently 6 months). The incidence of a palliative shunt at the time of repair decreased from 38% to 0%. Mortality of repair for the entire cohort was 2.6%, with mortality in the shunt era being 5.3% (n ⫽ 114) and mortality in the primary repair era being 0% (n ⫽ 113). Age at repair was divided into three groups: ⬍3 months, 3 to 11 months, and ⬎12 months. All the deaths occurred in those older than 12 months, and each had had a transannular patch as part of the repair. None of the children who died had prior palliation with a BT shunt. Independent factors associated with increased total hospital days were age ⬍3 months at repair, lower preoperative oxygen saturation, development of junctional ectopic tachycardia, and the presence of a palliative shunt at the time of definitive repair. Another physiologic marker of repair tolerance was time to lactate clearance, which was least in those ⬍3 months and greatest in those ⬎12 months of age (Fig 2). More ascites and longer intubation times were seen in those ⬍3 months of age. The use of preoperative -blockers increased as the incidence of a BT shunts decreased; however, there was no independent effect on outcome of physiologic parameters measured. A comparison of median cumulative hospital stay for infants ⬍3 months of age who had a systemic to pulmonary artery shunt followed by later repair and for infants ⬍3
Figure 2 Age-related hours to lactate normalization after repair of TOF.
G. Van Arsdell
130
Figure 3 A Cusum plot of operative mortality after repair of TOF from July 1982 through November 2004. The horizontal axis is the number of patients operated on. The vertical axis is the number of mortalities. The slope corresponds to a mortality rate. The inflection point corresponds to 1996, which is the time of the institutional policy shift to primary repair. Subsequent mortality is 0.6%.
month of age who had a primary repair demonstrated a trend toward a longer total hospital stay with palliation (median 32 days v median 21 days, P ⫽ .06).
Cumulative Outcomes Outcomes for repair of TOF from July 1982 through December of 2004 are shown as a cumulative summation curve in Fig 3. The inflection point in the slope of the curve corresponds with 1996 when the change in strategy occurred. Operative mortality before 1996 was 4.1% (that survival excludes mortality related to BT shunt palliation and interval mortality before repair and hence an underestimate of mortality). Operative mortality in the primary repair era was 0.6% (2/357).
Reasons for Improved Outcomes Based on past analysis of age-related outcomes, the dramatic improvement in survival was not predicted. The mortality improvement that occurred effectively came from removing the previously unrecognized risk factor of older age of repair. The concerns over increased mortality in the very young did not materialize. Present knowledge would suggest that later repair allowed development of further ventricular hypertrophy. We have since come to believe that ventricular hypertrophy is a significant risk factor for mortality in biventricular repair. There was no mortality in the older patients who had received a BT shunt. The volume load incurred from the BT shunt may have helped to mitigate the unfavorable volumeto-mass ratio seen in older patients, thereby protecting diastolic function at the time of repair.
Gene Expression Causes for Improved Outcomes analyzed,4
Gene expression data that we have mostly in TOF patients, demonstrate a pattern of cardioprotection and antihypertrophy in neonates as compared with older
infants and children. Two specific cardioprotective genes identified were atrial natriuretic polypeptide and insulinlike growth factor-2. Antigrowth genes (antihypertrophy) were small guanosine triphosphatase rap1, protein phosphatase-2, and others. Fibroblast growth factor shows downregulation in the neonate—another modulator of ventricular hypertrophy. It can be reasoned that younger age of repair, from a myocardial muscle standpoint, is better tolerated than older age of repair. Younger age of repair must be balanced against the lesser physiologic tolerance, in general, of a neonate to physiologic stress. We have therefore chosen to perform elective neonatal repair but to repair electively somewhere close to 6 months of age.
Mortality A brief discussion of the two mortalities in the current era is warranted. One child (who presented at ⬎1 year of age) developed an intraoperative cannulation site-induced dissection. Death was a consequence of the dissection. The second child had small pulmonary arteries, aortic stenosis, TOF, and biventricular outlet obstruction with biventricular hypertrophy. Initial treatment was balloon dilation of the aortic valve and the right ventricular outflow. The subsequent repair at several months of age required a fenestrated ventricular septal defect (VSD). Death was related to systolic and diastolic heart failure that was not successfully managed with ECMO (extracorporeal cardiac support).
Reasons for Repair at 6 Months Practice policy at the Hospital for Sick Children is protocol driven. As such, if the data suggested best outcomes for elective repair in the first 2 months of life, we would proceed with
An apology for primary repair of TOF that policy. Why have we not chosen this? Our experience and data demonstrate that repair at 6 months of age is very well tolerated. There is little development of restrictive physiology, minimal need for prolonged ventilation, and virtually no development of ascites. The use of propranolol has not been associated with postoperative problems. In contrast, although survival in the neonate and very young infant has been excellent, these patients more frequently develop restrictive physiology, frequently develop effusions, and in general require longer intubation and intensive care times (ie, there is increased morbidity as compared with those repaired at a later age). With enough patients, morbidity will translate into mortality at some point. Neonatal care has dramatically improved with the experience gained from management of transposition and hypoplastic left heart syndrome. The collateral benefit has been transferred to neonatal tetralogy repair as well; nevertheless, we do not believe elective neonatal repair of tetralogy is the best strategy just as we do not believe elective neonatal repair of large ASDs is the best strategy.
Restrictive Physiology A number of infants after repair of TOF seem to inexplicably become volume dependent and require quite some time to recover. We now know that this finding is caused by the development of restrictive physiology (this was not fully delineated in the 1980s and early 1990s). The sine quo non for diagnosis is antegrade blood flow in the pulmonary artery with atrial contraction as seen on echocardiography. Treatment is spontaneous ventilation so that negative respiratory pressure assists blood flow through the right heart. If extubation is not possible, minimal airway pressure ventilation is instituted, and both pleural spaces and the peritoneal cavity are drained if needed. Volume loading to central venous pressure of 15 or higher may be required. Occasionally, the chest needs to be opened to optimize diastolic function of the right heart and to minimize mean airway pressure. Generally, there is excellent systolic function. Inotropic support is avoided. Clear understanding of restrictive physiology is important to achieve excellent outcomes in the repair of TOF in the very young.
Pulmonary Artery Size The issue of pulmonary artery size is a legitimate concern for primary repair. The pulmonary arteries have been too small to accept a full cardiac output in approximately 2% of our patients. These patients are managed by VSD closure followed by fenestration with the intent to allow for pulmonary artery growth. Later VSD fenestration closure may be achieved in the interventional catheterization laboratory.
131
Conclusions Concerns over the increased risk of repair for TOF in young infants have proven to be ungrounded in our institution. Outcomes have improved dramatically with the shift to primary repair. This phenomenon can be explained by eliminating the risk of the BT shunt (it may be small and the incidence of risk may be institution dependent, but the risk is not zero) and by eliminating the ventricular hypertrophy-mediated risk of repair in the TOF patient over 1 year of age. Successful repair in the neonate and very young infant requires understanding and management of restrictive physiology. Because of the problems of restrictive physiology, we do not advocate elective neonatal repair. Problems with small pulmonary arteries are infrequent (1% to 2%) and can be managed with a fenestrated VSD. Finally, it seems that net hospitalization time is less with one-stage repair.
Caveats We can envision situations where it might be beneficial to first perform a BT shunt before repair. We believe a child who has a recent cerebral hemorrhage and tetralogy spells or poor saturations would have less net mortality risk if a BT shunt were performed as the means of treating hypoxia. Similarly, a child with sepsis, viral respiratory infection, or multiorgan issues might have less net mortality risk by the staged BT shunt approach. For each of these situations we would first try to aggressively medically manage and stabilize the child. An emergent intervention would be performed only if medical management failed. If balloon angioplasty of the right ventricular outflow tract/pulmonary valve complex seemed to be a viable possibility, we would opt to take this strategy before determining if a BT shunt is necessary. We have used balloon angioplasty for a handful of neonates and found it to be useful with respect to symptomatically improving the neonate and allowing for an elective repair at a more favorable age.
References 1. Vobecky SJ, Williams WG, Trusler GA, et al: Survival analysis of infants under age 18 months presenting with tetralogy of Fallot. Ann Thorac Surg 56:944-950, 1993 2. Gladman G, McCrindle BW, Williams WG, et al: The modified BlalockTaussig shunt: Clinical impact and morbidity in Fallot’s tetralogy in the current era. J Thorac Cardiovasc Surg 114:24-30, 1997 3. Van Arsdell GS, Maharaj GS, Tom J, et al: What is the optimal age for repair of tetralogy of Fallot? Circulation 102:III123-III129, 2000 (suppl III) 4. Konstantinov IE, Coles JG, Boscarino C, et al: Gene expression profiles in children undergoing cardiac surgery for right heart obstructive lesions. J Thorac Cardiovasc Surg 127:746-754, 2004
Historical and Present Surgical Strategy Age for planned repair of TOF at the Hospital for Sick Children, Toronto in the 1970s through the mid 1990s was 18 months. Infants who were symptomatic before 1 year of age received a Blalock Taussig (BT) shunt and then the usual repair at 18 months of age. In 1996, repair strategy was shifted to one of elective repair at 6 months of age. Earlier primary repair is now performed if the child is symptomatic.
Rationale for Change to Primary Repair The change in strategy was brought about by analysis of institutional outcomes at two different time points. For many years, our institutional data and data from other institutions had shown that younger age at repair was a risk factor for mortality. This concern and some isolated experiences led to continued use of palliation as the first line of therapy for babies ⬍1 year of age. However, palliation was not without its own problems— overcirculation (sometimes causing death), pulmonary artery distortion, shunt thrombosis, shunt seromas, and interval mortality before repair occurred. Problems associated with palliation allowed for an “extra” net mortality margin if one were to shift to primary repair in infants who were thought to be at higher risk. At our institu-
From the Hospital for Sick Children, Toronto, Ontario, Canada. Address reprint requests to Glen Van Arsdell, MD, Hospital for Sick Children, 555 University Ave, room 1525, Toronto, ON, M5G 1X8 Canada.
128
1092-9126/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.pcsu.2005.01.016
tion, the outcomes benefits from the change in strategy are clear. Along the way we have learned that some of the improvement in outcome may be specifically related to repairing before excessive development of ventricular hypertrophy (ie, earlier repair was actually a protection against an unfavorable outcome).
Outcomes in an Era of Palliation Vobecky et al1 published our data for repair of isolated TOF from 1978 through 1988. There were 237 infants with the entry criterion being diagnosis (not procedure). Actuarial survival at 10 years was 89.5%. There were a total of 22 deaths, of which 14 were pre-palliation, at palliation, or postpalliation but before repair. Operative mortalities occurred in 7 of 218 patients (3.2%). There was one late death in the cohort. When we looked at the incidence of a transannular patch, it seemed that a BT shunt did not have an influence: Transannular patch occurred in 48% for those with previous palliation and in 54% for those without previous palliation. Fifteen percent of those having a BT shunt required a pulmonary arterioplasty at the site of shunt insertion into the pulmonary artery. Based on mortality data alone, one could make an assumption that even if earlier repair were associated with a higher operative mortality, the net change in outcome would be zero provided the operative mortality was ⬍8.9% (14 pre-repair deaths ⫹ 7 operative deaths/237 ⫽ 8.9%). The net change in years of life lived would be greater for any operative mortality of ⬍8.9%. The data became even more compelling if one looked at the10-year survival for the 19 neonates requiring palliation (77%). This fact gave further weight to primary
An apology for primary repair of TOF
129
Institutional Policy Shift Synthesis of the above data and rationale led to a change in strategy for repair. Our current strategy is repair at 6 months of age if asymptomatic. A child with saturations of ⬍80% will undergo earlier repair, as would a child who has a tetralogy spell or a suggestion of a spell. Symptomatic children are placed on propranolol, and an elective date for repair is scheduled.
Outcomes for Primary Repair Analysis for Optimal Age of Repair for Tetralogy of Fallot Figure 1 Right pulmonary artery stenosis seen at the site of the previous shunt insertion. Some degree of stenosis can be seen in up to one third of shunted patients.
repair because there was an even greater added “margin of safety” for the very young. Nevertheless, in the late 1980s and early 1990s, it was not a given that primary repair of neonates and very young infants would be less than 10%. Neonatal repair, for most institutions, was just becoming a reality. However, the mortality “hurdle” to cross seemed to be approaching an era-adjusted reasonable number.
Outcomes Related to Blalock Taussig Shunts In a second analysis of outcomes related specifically to BT shunts for TOF, Gladman et al2 evaluated 60 infants who had BT shunts between 1990 and 1994. Each patient had had cardiac catheterization before repair of TOF. A comparison group of 68 nonpalliated but repaired TOF infants who had had cardiac catheterization was also analyzed.
Significant Findings in Palliated v Nonpalliated Infants The right pulmonary artery index was significantly smaller in the shunted infants than in those who were not shunted. The discrepancy was greater for those who received their shunt during the neonatal period (0.84 v 1.05). Shunt-related morbidity was not inconsequential—there was a 28% shunt related complication rate (excessive pulmonary blood flow, 28%; seroma, 1.5%; Horner syndrome, 3%; diaphragmatic palsy, 3%). One third of patients had more than mild distortion of the pulmonary artery where the shunt was inserted. There was one late death caused by shunt thrombosis. Overall survival in the palliated group was 90% v 97% for those not having palliation (P ⬍.05). Although one can argue that pulmonary artery distortion issues (Fig 1) may be surgeon dependent, problems with overcirculation and a definable incidence of shunt thrombosis are institution independent. The latter are related to intrinsic physiology of BT shunt palliation.
The change in strategy undertaken in Toronto yielded an opportune time to analyze optimal age for repair.3 From January 1993 to June 1998, 227 children underwent repair of isolated TOF. During that time, median age of repair dropped from 17 months to 8 months (it is currently 6 months). The incidence of a palliative shunt at the time of repair decreased from 38% to 0%. Mortality of repair for the entire cohort was 2.6%, with mortality in the shunt era being 5.3% (n ⫽ 114) and mortality in the primary repair era being 0% (n ⫽ 113). Age at repair was divided into three groups: ⬍3 months, 3 to 11 months, and ⬎12 months. All the deaths occurred in those older than 12 months, and each had had a transannular patch as part of the repair. None of the children who died had prior palliation with a BT shunt. Independent factors associated with increased total hospital days were age ⬍3 months at repair, lower preoperative oxygen saturation, development of junctional ectopic tachycardia, and the presence of a palliative shunt at the time of definitive repair. Another physiologic marker of repair tolerance was time to lactate clearance, which was least in those ⬍3 months and greatest in those ⬎12 months of age (Fig 2). More ascites and longer intubation times were seen in those ⬍3 months of age. The use of preoperative -blockers increased as the incidence of a BT shunts decreased; however, there was no independent effect on outcome of physiologic parameters measured. A comparison of median cumulative hospital stay for infants ⬍3 months of age who had a systemic to pulmonary artery shunt followed by later repair and for infants ⬍3
Figure 2 Age-related hours to lactate normalization after repair of TOF.
G. Van Arsdell
130
Figure 3 A Cusum plot of operative mortality after repair of TOF from July 1982 through November 2004. The horizontal axis is the number of patients operated on. The vertical axis is the number of mortalities. The slope corresponds to a mortality rate. The inflection point corresponds to 1996, which is the time of the institutional policy shift to primary repair. Subsequent mortality is 0.6%.
month of age who had a primary repair demonstrated a trend toward a longer total hospital stay with palliation (median 32 days v median 21 days, P ⫽ .06).
Cumulative Outcomes Outcomes for repair of TOF from July 1982 through December of 2004 are shown as a cumulative summation curve in Fig 3. The inflection point in the slope of the curve corresponds with 1996 when the change in strategy occurred. Operative mortality before 1996 was 4.1% (that survival excludes mortality related to BT shunt palliation and interval mortality before repair and hence an underestimate of mortality). Operative mortality in the primary repair era was 0.6% (2/357).
Reasons for Improved Outcomes Based on past analysis of age-related outcomes, the dramatic improvement in survival was not predicted. The mortality improvement that occurred effectively came from removing the previously unrecognized risk factor of older age of repair. The concerns over increased mortality in the very young did not materialize. Present knowledge would suggest that later repair allowed development of further ventricular hypertrophy. We have since come to believe that ventricular hypertrophy is a significant risk factor for mortality in biventricular repair. There was no mortality in the older patients who had received a BT shunt. The volume load incurred from the BT shunt may have helped to mitigate the unfavorable volumeto-mass ratio seen in older patients, thereby protecting diastolic function at the time of repair.
Gene Expression Causes for Improved Outcomes analyzed,4
Gene expression data that we have mostly in TOF patients, demonstrate a pattern of cardioprotection and antihypertrophy in neonates as compared with older
infants and children. Two specific cardioprotective genes identified were atrial natriuretic polypeptide and insulinlike growth factor-2. Antigrowth genes (antihypertrophy) were small guanosine triphosphatase rap1, protein phosphatase-2, and others. Fibroblast growth factor shows downregulation in the neonate—another modulator of ventricular hypertrophy. It can be reasoned that younger age of repair, from a myocardial muscle standpoint, is better tolerated than older age of repair. Younger age of repair must be balanced against the lesser physiologic tolerance, in general, of a neonate to physiologic stress. We have therefore chosen to perform elective neonatal repair but to repair electively somewhere close to 6 months of age.
Mortality A brief discussion of the two mortalities in the current era is warranted. One child (who presented at ⬎1 year of age) developed an intraoperative cannulation site-induced dissection. Death was a consequence of the dissection. The second child had small pulmonary arteries, aortic stenosis, TOF, and biventricular outlet obstruction with biventricular hypertrophy. Initial treatment was balloon dilation of the aortic valve and the right ventricular outflow. The subsequent repair at several months of age required a fenestrated ventricular septal defect (VSD). Death was related to systolic and diastolic heart failure that was not successfully managed with ECMO (extracorporeal cardiac support).
Reasons for Repair at 6 Months Practice policy at the Hospital for Sick Children is protocol driven. As such, if the data suggested best outcomes for elective repair in the first 2 months of life, we would proceed with
An apology for primary repair of TOF that policy. Why have we not chosen this? Our experience and data demonstrate that repair at 6 months of age is very well tolerated. There is little development of restrictive physiology, minimal need for prolonged ventilation, and virtually no development of ascites. The use of propranolol has not been associated with postoperative problems. In contrast, although survival in the neonate and very young infant has been excellent, these patients more frequently develop restrictive physiology, frequently develop effusions, and in general require longer intubation and intensive care times (ie, there is increased morbidity as compared with those repaired at a later age). With enough patients, morbidity will translate into mortality at some point. Neonatal care has dramatically improved with the experience gained from management of transposition and hypoplastic left heart syndrome. The collateral benefit has been transferred to neonatal tetralogy repair as well; nevertheless, we do not believe elective neonatal repair of tetralogy is the best strategy just as we do not believe elective neonatal repair of large ASDs is the best strategy.
Restrictive Physiology A number of infants after repair of TOF seem to inexplicably become volume dependent and require quite some time to recover. We now know that this finding is caused by the development of restrictive physiology (this was not fully delineated in the 1980s and early 1990s). The sine quo non for diagnosis is antegrade blood flow in the pulmonary artery with atrial contraction as seen on echocardiography. Treatment is spontaneous ventilation so that negative respiratory pressure assists blood flow through the right heart. If extubation is not possible, minimal airway pressure ventilation is instituted, and both pleural spaces and the peritoneal cavity are drained if needed. Volume loading to central venous pressure of 15 or higher may be required. Occasionally, the chest needs to be opened to optimize diastolic function of the right heart and to minimize mean airway pressure. Generally, there is excellent systolic function. Inotropic support is avoided. Clear understanding of restrictive physiology is important to achieve excellent outcomes in the repair of TOF in the very young.
Pulmonary Artery Size The issue of pulmonary artery size is a legitimate concern for primary repair. The pulmonary arteries have been too small to accept a full cardiac output in approximately 2% of our patients. These patients are managed by VSD closure followed by fenestration with the intent to allow for pulmonary artery growth. Later VSD fenestration closure may be achieved in the interventional catheterization laboratory.
131
Conclusions Concerns over the increased risk of repair for TOF in young infants have proven to be ungrounded in our institution. Outcomes have improved dramatically with the shift to primary repair. This phenomenon can be explained by eliminating the risk of the BT shunt (it may be small and the incidence of risk may be institution dependent, but the risk is not zero) and by eliminating the ventricular hypertrophy-mediated risk of repair in the TOF patient over 1 year of age. Successful repair in the neonate and very young infant requires understanding and management of restrictive physiology. Because of the problems of restrictive physiology, we do not advocate elective neonatal repair. Problems with small pulmonary arteries are infrequent (1% to 2%) and can be managed with a fenestrated VSD. Finally, it seems that net hospitalization time is less with one-stage repair.
Caveats We can envision situations where it might be beneficial to first perform a BT shunt before repair. We believe a child who has a recent cerebral hemorrhage and tetralogy spells or poor saturations would have less net mortality risk if a BT shunt were performed as the means of treating hypoxia. Similarly, a child with sepsis, viral respiratory infection, or multiorgan issues might have less net mortality risk by the staged BT shunt approach. For each of these situations we would first try to aggressively medically manage and stabilize the child. An emergent intervention would be performed only if medical management failed. If balloon angioplasty of the right ventricular outflow tract/pulmonary valve complex seemed to be a viable possibility, we would opt to take this strategy before determining if a BT shunt is necessary. We have used balloon angioplasty for a handful of neonates and found it to be useful with respect to symptomatically improving the neonate and allowing for an elective repair at a more favorable age.
References 1. Vobecky SJ, Williams WG, Trusler GA, et al: Survival analysis of infants under age 18 months presenting with tetralogy of Fallot. Ann Thorac Surg 56:944-950, 1993 2. Gladman G, McCrindle BW, Williams WG, et al: The modified BlalockTaussig shunt: Clinical impact and morbidity in Fallot’s tetralogy in the current era. J Thorac Cardiovasc Surg 114:24-30, 1997 3. Van Arsdell GS, Maharaj GS, Tom J, et al: What is the optimal age for repair of tetralogy of Fallot? Circulation 102:III123-III129, 2000 (suppl III) 4. Konstantinov IE, Coles JG, Boscarino C, et al: Gene expression profiles in children undergoing cardiac surgery for right heart obstructive lesions. J Thorac Cardiovasc Surg 127:746-754, 2004